To achieve an efficient production of aerosol tops from T-3 (Temper-3) plate or even harder plate, it is absolutely necessary to have a smooth edge without any shear or tear marks on the opening of the upper cylindrical part. An absence of a perfectly smooth edge will result into a cracked curl in the subsequent curling operation which will make the component a reject. With the four conventional piercing methods presently used, the means of counter acting the cracking or splitting tendency of the curls during the curling operation, is to use relatively soft plate. This would be mostly T-1 plate.
T-3 plate is about 8% cheaper than T-1 plate. Due to the fact that the harder plate (T-3 or T-4) has a greater tensile strength, thinner plate can be used without reducing the inside pressure resistance of the aerosol top. This results into another 6% material cost reduction.